Rotary photogravure printing apparatus



A ril 3, 1962 A. M. HALLEY 3,027,832

ROTARY PHOTOGRAVURE PRINTING APPARATUS Filed June 25, 1959 Attorneys United States Patent C) 3,027,832 ROTARY PHOTOGRAVURE PRINTING APPARATUS Angus Murray Halley, Moseley, Birmingham, England,

assignor to James Halley & Sons Limited, West Bromwich, England, a British company Filed June 23, 1959, Ser. No. 822,305 Claims priority, application Great Britain July 5, 1958 7 Claims. (Cl. 101-447) This invention relates to improvements connected with rotary photogravure printingapparatus and more specifically is directed to a rotary photogravure printing apparatus of the kind wherein the printing cylinder is supported in a cradle which is fulcrumed on the frame of the apparatus and wherein the cradle can be raised or lowered by means of pneumatically or hydraulically operated ram means in order to effect the contact of the printing cylinder with the co-acting impression cylinder with the requisite pressure.

Experience has shown that in contrast to the relatively large pressures employed between the printing and impression cylinders for printing most materials, when printing upon very thin materials, such as, for example, aluminium foil, cellulose film or polythene film, light printing pressures are desirable. Heretofore in processing such thin materials in the aforesaid kind of printing apparatus the pressure has been reduced in the supply line to the ram means through the agency of a reducing valve whereby the thrust which is in turn applied by the rams to the cradle and cylinders is proportionately diminished. It is found in practice that such a procedure may give rise to large variations in the printing pressure due to relatively small variations in the supply line pressure since, for example, a fall in pressure of 1 lb. square inch from 4 to 3 lbs. per square inch in the supply line when operating at low pressures represents alternation in the printing pressure. Such a variation in the printing pressure can seriously affect the register between the colours in a multi-colour printing press.

This invention has for its object to overcome the aforesaid difiiculty by the incorporation in the printing machine of ram means adapted to furnish both relatively light and heavy printing pressures when energised by the connection of a relatively high pressure supply line to the ram means, whereby more constant light printing pressures may be obtained than has heretofore been achieved by the above mentioned method of diminishing the pressure of the supply line to the rams.

Accordingly the invention consists of a rotary photogravure printing apparatus of the kind wherein the printing cylinder is supported in a pivotally mounted cradle which can be rocked by fluid operated ram means to determine the printing pressure, characterised in that said ram means comprises at least one double-acting ram wherein the cylinder of the ram is connected on opposite sides of the piston to a common relatively high pressure air supply line through control valve means so that a relatively high printing pressure is furnished by introducing air under pressure into the cylinder on one side of the piston only whereas a relatively light printing pres sure is furnished by introducing air under pressure into the cylinder on both sides of the piston, the magnitude of the light pressure being determined by a cross-sectional area differential between opposite sides of the piston.

Preferred means for carrying the invention into practice will now be described with reference to the accompanying drawing which illustrates diagrammatically a side elevation of a rotary photogravure printing apparatus according to the invention.

In a convenient embodiment of the invention, a cradle 1 of general rectangular form in plan is fulcrumed adjacent two of its corners at A on the frame -2 of the printing machine and is supported adjacent its opposite or free corners at B by two pneumatic double-acting rams generally designated X. The ram cylinders 3 are anchored at C to the frame of the machine and the ram pistons 4 are coupled through connecting rods 5 to the free corners of the cradle. Thus the upward thrusts of the rams X are arranged to counteract the weight of the cradle 1 to control the contact pressure which obtains between the printing cylinder 5 rotatably mounted on the cradle and the superimposed impression cylinder 7 rotably mounted on the frame.

According to the invention, the cylinder 3 of each ram X is connected to its two ends on opposite sides of the piston contained within the cylinder through a pair of branch lines 8 and 9 and a control valve 10 to a common high pressure supply line 11. Line 11 is in turn connected through a manually controlled pressure reducing valve .12 to a source of compressed air (not shown). The branch air line 8 which is connected to the lower end of each cylinder 3, i.e., beneath the piston, has permanent communication through the control valve 10 with the reducing valve =12 during the operation of the machine, whereas the upper end of each cylinder 3, i.e. above the piston, is connected to the high pressure supply line 11 in one setting of the control valve 10 which admits of the connection or disconnection of the upper sections of the cylinders from the supply line 1-1 at will.

In operation, when the upper end of each cylinder 3 is disconnected from the supply line 11 by the control valve 10, only the lower sections 13 of the rams X are energised to impart a high pressure upward thrust through the connecting rods 5 on the cradle :1 to furnish a high printing pressure. It will be appreciated, however, that due to the differential area of the upper and lower faces of the piston of each ram which is obtained due to the presence of the piston rod 15 extending from the upper face of the piston and through the upper section 14 of each cylinder 3, the connection of the supply line 11 to both the upper and lower sections 14 and 13 of each ram cylinder will result in a high pressure upward thrust on the underside of each piston and a somewhat lower downward thrust on the upper face of each piston. The differential effect is the furnish a relatively light upward thrust upon the cradle. Thus, if the high and low pressure ranges are required to be furnished by the rams in say the ratio of 7:1, the piston rods 15 must occupy one seventh of the cross-sectional area of the upper sections 14 of their respective cylinders.

Desirably the manually controlled reducing valve 12 is provided with a pressure gauge =16, which is conveniently calibrated in alternative low and high ranges to provide an indication of the thrust imparted to the cradle by the rams in the alternative settings of the control valve 10.

It will be appreciated that the inherent compressibility of the air employed for energising the rams X confers a resiliency in the cradle support which is particularly advantageous in operation say, for example, when a joint in a thick web of material passes through the nip between printing and impression cylinders.

I claim:

1. In a rotary printing press, an impression cylinder mounted for rotation about an axis, a printing cylinder mounted for rotation about an axis below and parallel to that of the impression cylinder, a support for said printing cylinder mounted for movement to shift said printing cylinder toward and away from said impression cylinder, and means for shifting said support to either urge said cylinders together with relatively heavy normal printing pressure or to urge said cylinders together with relatively light printing pressure for printing very thin materials, said support shifting means comprising a fluid actuated ram having a substantially vertically disposed difierential area piston assembly having a relatively large piston area and an opposed smaller piston area operatively connected to the support, means providing a high fluid pressure supply line, and control means for applying fluid under pressure from said line only to the larger area of said piston assembly to apply said relatively high printing pressure and to both areas of said piston assembly to apply said relatively light printing pressure.

2. In the rotary printing press defined in claim 1, said support being a cradle pivoted adjacent one end and having two of said rams connected at an opposite end.

3. In the rotary printing press defined in claim 1, said control means comprising a selector valve shiftable to selectively connect said line to the larger area side only of said piston assembly or to both sides.

4. In the rotary printing press defined in claim 1, said piston assembly comprising a compound piston having a larger downwardly facing area.

5. In a rotary printing press, an impression cylinder mounted for rotation about an axis, a printing cylinder mounted for rotation about an axis below and parallel to that of the impression cylinder, a support for said printing cylinder, and means for shifting said support to either urge said cylinders together with relatively heavy normal printing pressure or to urge said cylinders together with relatively light printing pressure for printing very thin materials, said support shifting means comprising a fluid actuated ram having a differential area piston assembly operatively connected to the support, means providing a high fluid pressure supply line, control means for applying fluid under pressure from said line only to the larger area of said piston asembly to apply said relatively high printing pressure or to both areas of said piston assembly to apply said relatively light printing pressure, and means in said line for varying the pressure of the fluid supplied to said control means.

6. In the rotary printing press defined in claim 5, a dual range pressure gauge in said line at the output side of said pressure varying means, said gauge being calibrated in two ranges corresponding to high and low printing pressure forces exerted by said ram.

7. In the rotary printing press defined in claim 1, said high fluid pressure supply line being connected to a source of pneumatic pressure.

References Cited in the file of this patent UNITED STATES PATENTS 579,432 Harrison Mar. 23, 1897 844,349 Hale Feb. 19, 1907 844,350 Hale Feb. 19, 1907 1,327,036 Ogsbury Oct. 13, 1931 2,138,142 Dietrich Nov. 29, 1938 2,267,380 Tyler Dec. 23, 1941 

